Continuity mistake: Adaline takes the glass of liquor from Ellis' hand and finishes it. Once she walks out the door the glass is next to Ellis again, and when she appears outside it's filled again.
Other mistake: Near the end, Ellen Burstyn is holding the new puppy, referring to the dog as a female. Right after that, she is talking to Ellis with the puppy there, and they refer to the dog as a male.
Chosen answer: It was because she had used so many fake I.D. the F.B.I. had become suspicious, possibly believing she was involved in some type of criminal activity, which is often why people assume different identities.
raywest ★